<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        html, body {
            height: 100%;
            width: 100%;
        }
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        body {
            display: flex;
            flex-direction: column;
        }
        header, footer {
            height: 100px;
            background: #eee;
        }
        .main {
            flex: 1;
            display: flex;
        }
        .main .left, .main .right {
            width: 15%
        }
        .main .left {
            background: #f00;
        }
        .main .right {
            background: #00f;
        }
        .main .center {
            flex: 1;
        }
        @media screen and (min-width: 1200px) {
            h1 {
                font-size: 48px;
            }
            .main .center {
                background: orange;
            }
        }
        @media screen and (min-width: 800px) and (max-width: 1200px) {
            h1 {
                font-size: 30px;
            }
            .main .center {
                background: #fcf;
            }
        }
        @media screen and (max-width: 800px) {
            h1 {
                font-size: 18px;
            }
            .main .center {
                background: #aa0;
            }
        }
    </style>
</head>
<body>
    <header>This is head</header>
    <section class="main">
        <section class="left"><h1>left</h1></section>
        <section class="center"><h1>center</h1></section>
        <section class="right"><h1>right</h1></section>
    </section>
    <footer>This is foot</footer>
</body>
</html>